The present invention relates to a power distributing mechanism applicable in a vehicle of an all wheel drive type, of which front wheels are used as steering wheels, such as ordinary cars, off-road automobiles, industrial vehicles and construction vehicles.
Generally, a vehicle of an all wheel drive type is designed to transmit a power to front and rear wheels through a transmission and to control steering by front wheels. It has been well known that when such vehicle of the front-steering type is steered, rotation speed of the front wheel becomes larger than that of the rear wheels. This discrepancy in speed is a result of the rear wheels being closer to the central point of rotary motion as the vehicle turns. The front wheels during steered motion travel a larger distance on the outer circumference of vehicle rotary motion than do the rear wheels on a rotary path. The effect is that the rear wheels tend to shift direction in place while the front steering wheels roll to reach a new orientation.
Therefore, when the power is supplied directly to the front and rear wheels from the transmission, the difference of above rotation speed during the steering causes a slip of tires, which results in a power loss and wearing of tires, and may cause breakage of the driving system. In order to avoid them, some vehicles have employed differential mechanisms to appropriately distribute the torque to the front and rear wheels. However, in such vehicles, when a wheel slips on a rough land such as a snow-covered road, a sufficient torque can not be transmitted to other wheels without slipping, so that those vehicles may disadvantageously looser driving stability.
Further, in an usual driving on a public road, there is a large loss of the mechanical energy when the all wheels are driven, and thus, two wheel driving is desired. Therefore, it is necessary or desirable to provide a selector device for selecting the two wheel driving and the four wheel driving.
Accordingly, it is an object of the invention to provide a power distributing mechanism, wherein a power to the front wheels can be cut off only when the front wheels rotates faster than the rear wheels in the all wheel driving condition.
Other object of the invention is to provide a mechanism, wherein a structure is simple without a complicated mechanism such as a non-spin differential mechanism, and thus, the manufacturing cost can be reduced.
Another object of the invention is to provide a mechanism, where in a selecting or switching operation between a two-wheel driving and an all-wheel driving can be performed both in a running condition and a stopping condition of a vehicle.
According to the invention, a power distributing mechanism for a vehicle of a front and rear wheel driving type wherein a driving system is designed to transmit a power through a transmission to front and rear wheels and the front wheels are designed to be steered, comprises a shaft for the rear wheels adapted to connect to a driving mechanism; a shaft for the front wheels coaxially adjacent to the shaft for the front wheels; a driving rotator having outer teeth and connected to the outer periphery of the shaft for the rear wheels; a driven rotator having outer teeth and axially slidably connected to the outer periphery of the shaft for the front wheels; a forcing means for elastically forcing the driven rotator toward the driving rotator; a cylindrical intermediate member disposed around both rotators and having inner teeth engageable with the outer teeth of the respective rotators with circumferential spaces therebetween; and a braking means for applying a braking force to the rotating intermediate member; said both rotators being provided at the end surface portions facing to each other with projections which are adapted to generate axially opposite forces to move away and disengage the driven rotator from the intermediate member when a relative rotation is generated between both rotators.
Other and further objects, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.